Method and peer network for ascertaining the peer network originating station for a file

ABSTRACT

Files which are available for dissemination in a controlled peer-to-peer network are provided with a watermark comprising a large number of watermark elements. Upon download, the composition of the parts of the file which are obtained from a plurality of source stations provides a new watermark which can clearly be associated with the target station. By storing information about forwarded watermark elements of a network server, it is possible to reconstruct for each file the network station from which this file originates.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and hereby claims priority to GermanApplication No. 10 2005 058 006.8 filed on Dec. 5, 2005 and PCTApplication No. PCT/EP2006/067678 filed on Oct. 23, 2006, the contentsof which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The invention relates to a method for determining the originatingstation of a file in a peer network.

The exchange of information in present-day networks, such as theInternet for example, generally operates according to the client-serverprinciple. This means that a computer or a group of computers whichrepresent a server make information available. Other network nodes orcomputers which require this information download it from the server.

This method has the disadvantage that the load involved in distributingthe information lies solely on the server. The server must respond toall requests for a specific piece of information itself and send theinformation to the corresponding clients that submitted the request.This is particularly disadvantageous when a particular piece ofinformation is new and consequently is requested by very many clientsover a short period of time. An example of such information is asoftware update, for example an update for an operating system. In thecase of such information it is necessary to provide a particularlypowerful server which has the loadbearing capacity to handle the loadimposed by the requests. A server of this kind is cost-intensive.However, if, after a short time, the number of requests for theinformation drops off, the full capacity of the server is no longerbeing used. The investment in the high-performance server system istherefore excessive after a short period of time.

An alternative that avoids the disadvantages mentioned are peernetworks. These are networks composed of stations that are of equalstatus. An example of a peer network of this kind are the currentlycommon peer-to-peer networks. Such peer networks are generally logicalnetworks which are typically formed when a plurality of stations of alarger network, such as e.g. Internet, join forces to share resources.

The most important characteristic of the peer networks is that eachstation can act simultaneously as server and as client. This means thateach station can request information and also make informationavailable. Thus, if new information, such as a software update, forexample, is to be made available, each station in a peer networkautomatically offers that part of the software update that is alreadystored on said station for downloading to other stations of the peernetwork.

Generally a server continues to be necessary, the server making theinformation, such as the software update for example, available to thepeer network at least initially. However, the main load of informationdistribution now no longer lies with this server, but with the nodes ofthe peer network. These peer nodes are generally computers of users ofthe network. These computers are loaded with the task of informationdistribution to the extent possible according to the capability of theirconfiguration. This means that the additional load generally goesunnoticed by the users of these computers and that the load distributiontherefore is simply a better utilization of already existing resources.

Peer networks can also be used for disseminating multimedia content.Such multimedia content can be music or videos, for example. In thiscase it is ensured in a controlled peer network that the owners of therights to the distributed content are remunerated in accordance with thedistribution. It is not desirable in this case that content purchased inthe peer network is disseminated outside of the peer network. If thishappens nonetheless, for example in a further, uncontrolled peernetwork, the origin of a file distributed further in such a way can nolonger be identified.

SUMMARY

Our potential object is to specify a way to determine the origin of afile from a peer network.

The inventors propose a method in which the following steps are carriedout:

marking of files in a peer network with watermarks unique to stations ofthe peer network, said watermarks including a plurality ofsub-watermarks;

comparison of a first watermark, determined from the file, of the firstwatermark with the unique watermarks;

determining of the peer network originating station from the result ofthe comparison.

In order to identify the originating station of the file, the watermarkthat is contained in it itself is therefore determined. Furthermore saidwatermark is compared with the unique watermarks which permit aninference to be drawn as to the originating station. From the result ofthe comparison it is possible to conclude whether the file originatesfrom a station of the peer network or not.

What is understood by a watermark in a digital context is an additionalpiece of information which is inserted into an arbitrary file or a partof the file. In the case of a file having multimedia content, which istherefore intended for presentation to a human user, this additionalinformation may be more or less visible. Thus, there are clearly visiblewatermarks such as manufacturer logos, for example. But there are alsowatermarks which are not noticeable to the human viewer or listener.Watermarks of said kind can be implemented, for example, by using theleast significant bit of each byte in unencoded content for introducingthe additional information, i.e. the watermark. A change to the leastsignificant bit is not visible or audible to the human observer.

What is meant by watermark in this context is the totality of theadditional information that is incorporated into a file in the peernetwork. By sub-watermark what is understood is the information whichcan be taken from a small part of a file. For example, a sub-watermarkcan comprise a small number of bytes. This means that what is understoodby a sub-watermark is the additional information which is contained in ablock of a few bytes in length in a file.

In an advantageous embodiment and development, information relating toparts of files transmitted in the peer network is stored, saidinformation including at least the sub-watermarks contained in thetransmitted parts of the files.

Files are generally transferred in parts in peer networks. When theparts are assembled, a complete file is thus obtained once again. Thetransmitted parts of files therefore also include transmitted completefiles.

In addition to the transmission of files or parts of files in the peernetwork, therefore, information about transmitted parts is stored. Bythis it is possible to trace the transmission of the sub-watermarks inall the transmissions taking place in the peer network. This enables thewatermark of each file to be reconstructed at every station of the peernetwork.

The stored information includes therein at least the sub-watermarkscontained in parts of files transmitted in each case. This means that,for example, the watermark per se is stored, i.e. the additionalwatermark information which is incorporated into files in the form ofthe watermark. Alternatively it is also possible to store an identifierof the watermark. For example, different watermarks can be used whichare identified by a sequential number. In this case it is sufficient tostore the sequential number for a sub-watermark.

In an advantageous embodiment and development, information abouttransmitted parts is transmitted to a storage station. The storagestation is a station inside or outside the peer network which storessuch information relating to parts of files transmitted in the peernetwork. It can be a server installed for this purpose, or else astation of the peer network, for example. The centralized storage of theinformation reduces the risk of misuse and allows permanent access tothe data.

In this arrangement the information is advantageously transmitted fromthe source or destination station to the storage station. It isparticularly advantageous if the information is transmitted by bothstations. If both destination and source station send the information tothe storage station, the degree of resilience with regard to errors isincreased on the one hand and on the other hand the risk of misuse onthe part of the destination station ZS is reduced.

In an advantageous alternative, the information is stored in adecentralized manner in the peer network. In this way it is possible todistribute the overhead arising from the storage of the informationamong the stations of the peer network. As a result the resources of thepeer network are used more efficiently and the storage overhead isreduced.

The following steps are advantageously carried out for marking files inthe peer network:

providing at least two versions of the files, each of which is providedwith at least one watermark having a plurality of sub-watermarks, thewatermarks of the versions being different, in the peer network,

during the transmission of at least a part of the file from a sourcestation to a destination station in the peer network, transfer of thesub-watermarks in the part of the file from the source station to thedestination station.

In the first step, therefore, at least two versions of files are madeavailable in the peer network. In this case the versions made availablecontain different watermarks. This means that at least some of thesub-watermarks are different from one another, though ideally a largenumber of the sub-watermarks or even all the watermarks are different.

If parts of such files made available are now transmitted from a sourcestation to a destination station in the peer network, the sub-watermarkscontained in the parts of the files are transferred and consequently arealso present in the parts of the files on the destination station.

When a file is transmitted in a peer network, said file is generallyobtained from a plurality of sources. Since multiple versions of thefile having different watermarks are available in the peer network, saidwatermarks become intermingled during the transmission to thedestination station because the respective sub-watermarks of thedifferent versions are transmitted together with the corresponding partsof the file. This results in a version of the file having a newwatermark. Given a sufficiently large number of sub-watermarks in afile, each new watermark produced in this way at a new destinationstation is unique and can be used for identifying and determining saiddestination station.

In an advantageous development, the versions of files are generated bycreating two copies of each of the files and providing them withdifferent watermarks. The generated versions are then made available onat least one node in the peer network. In this case it is also possiblethat two or more provider stations in the peer network are basicallyresponsible for providing the versions for new files.

Alternatively it is also possible that in order to provide the versionsthe files are made available without a watermark. If parts of the fileswhich do not yet contain any watermarks are now transmitted, awatermark, including one, two or more sub-watermarks, is addedautomatically to these parts. This alternative has the advantage that aplurality of different versions are generated automatically and at thesame time the load involved in their generation is once again sharedamong the network nodes of the peer network.

In a further advantageous embodiment and development it is ascertainedwhether the transmission of at least one large part of a file isperformed by only one source station (“a primary source station”) and inthis case the sub-watermarks are redefined in at least the large part ofsaid file at the destination station. The sub-watermarks can be modifiedin the process, i.e. the new sub-watermarks are related to thetransmitted sub-watermarks. Alternatively, they can also be definedindependently of the transmitted sub-watermarks, by random selection forexample.

This advantageously avoids a situation in which, when a file istransmitted by a small number of source stations or in the worst case byonly one source station, the watermark of said file is transferred tothe destination station with no or only minor changes. This in turnmaintains the uniqueness of the identification by the watermark.

In an advantageous development, only one version of the file is madeavailable in the peer network for the purpose of providing the versions.The first transmissions of said file are then effected automatically byonly one or a small number of sources and the transmitted files areassigned new sub-watermarks. In this way many different versions of saidfile are advantageously generated automatically.

According to the method, a very large number of sub-watermarks arepreferably used for the watermark. By this means the uniqueness of thewatermark is guaranteed even in the case of a very large number of peernetwork nodes and therefore file versions.

It is possible for all the sub-watermarks to be the same size. Thissimplifies processing and evaluation.

Alternatively it is also possible for the sub-watermarks to be ofdifferent sizes. This has the advantage that a misuse due to deliberateremoval of the watermarks from a file is made more difficult.

Preferably the sub-watermarks can at least partially overlap. This meansthat a plurality of watermarks are inserted at least in certain bytes ofa file. This has the advantage that the security of the watermarks isincreased and their removal rendered more difficult.

Preferably the transmission of the part of the file from the sourcestation to the destination station takes place in packets in such a waythat at least one sub-watermark or all sub-watermarks are transmitted infull in the part of the file. In this way it is guaranteed that thesub-watermarks remain identifiable even after the transmission from thesource station to the destination station.

For this purpose the size of the packets and the size of a sub-watermarkare preferably chosen such that the packet size is a common integermultiple of the sizes of the sub-watermarks. In this case the packetsize can also be equal to the size of the sub-watermarks.

The peer network includes a plurality of network stations. These canoperate as source station and as destination station for thetransmission of at least parts of files. The network stations areembodied to perform the marking and transmission of information to thestorage station.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention willbecome more apparent and more readily appreciated from the followingdescription of the preferred embodiments, taken in conjunction with theaccompanying drawings of which:

FIG. 1 shows a peer network comprising three source stations, adestination station and a storage station.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to like elementsthroughout.

In the exemplary embodiment it is shown how it is ascertained for a filefrom which station in a peer network PN said file originates. For thispurpose it is basically necessary to mark the files that are distributedin the peer network. Furthermore the marking must be effectedpreventively. If a search is made as to the origin of a file, no furthermarking can be done at this time. It is also necessary to have knowledgeabout the markings in the files distributed in the peer network PN. Inthe exemplary embodiment this knowledge is stored in a central storagedevice.

FIG. 1 shows how the marking with watermarks is performed in anexemplary peer network PN. In this example all the distributed files aremarked. Alternatively it is possible to mark only certain files, videofiles for example, although in that case only the origin of said markedfiles can then be determined.

The exemplary peer network PN contains four peer network nodes, of whichin this example three operate as source stations QS1 . . . 3, and one asa destination station ZS. As usual in peer networks, it is also possiblein this case for each station to operate as a source or destinationstation.

The destination station would now like to receive a file from the peernetwork PN. Said file has been made available in the peer network PN inthree different versions with three different watermarks W1 . . . 3.These are contained at least in parts on the source stations QS1 . . .3.

Parts of the file are now transmitted in data transmissions U from thesource stations QS1 . . . 3 to the destination station ZS. In this casethe source stations QS1 . . . 3 have themselves stored different partsof the file.

These different parts contain different watermarks W1 . . . 3. In thiscase the watermarks W1 . . . 3 include sub-watermarks which areidentified here by different digits. In this exemplary embodiment asub-watermark of this kind extends over 1 KB of the file in each case.In the transmissions U, the file is therefore transmitted in 1 KB-sizedblocks in each case, each containing a complete sub-watermark.

As a result of the transmissions U from the different source stationsQS1 . . . 3, a new watermark WZ is generated at the destination station,said new watermark being produced from the different sub-watermarks ofthe watermarks W1 . . . 3 in the source stations QS1 . . . 3.

Information I is transmitted from the source stations QS1 . . . 3 to thestorage station S simultaneously with the transmissions U. In analternative embodiment variant the information I can also be transmittedby the destination station ZS or additionally by the destination stationZS to the storage station S. The information I contains thesub-watermarks transmitted in the transmissions U together with arespective indication of the position of the sub-watermark in the file.As a result the storage station S is able, after the transmission of thecomplete file to the destination station ZS, to specify the watermark WZresulting there.

In an alternative embodiment variant the information I is stored only inthe respective source station QS1 . . . 3. If the information I isrequired for identification purposes, the information I, storednon-centrally in this case, is retrieved from the stations of the peernetwork PN. In a further alternative the destination station ZS, afterreceiving the complete file, sends information I to the storage stationS, the information I in this case containing the complete new watermarkWZ. It is also possible to combine the aforementioned alternatives. Ifboth destination and source station ZS, QS1 . . . 3 send the informationI about the transmitted file to the storage station S, this increasesthe resilience with regard to errors on the one hand and on the otherhand reduces the risk of misuse on the part of the destination stationZS.

In this case the sub-watermarks are stored and/or transmitted in such away that in one alternative the watermark per se, i.e. the additionalinformation embedded in files by the watermark, is stored ortransmitted. Alternatively, an identifier for a watermark can also betransmitted and/or stored. For example, a sequential number for thewatermarks used in the peer network PN can be stored here.

If the file is now distributed outside of the peer network PN, it can beascertained, by comparing the watermark WZ of the file with theinformation of the storage station S, from which originating stationthis file has come.

It is possible in this case that some of the sub-watermarks cannot bereconstructed correctly by the storage station S, due to errors in thetransmission U to the destination station ZS or to the storage stationS, for example. By virtue of the large number of sub-watermarks it is,however, ensured that such a great number of possibilities forwatermarks exists that even a similarity of a watermark to theinformation I stored in the storage station S can be rated as equality.According to this example, a film 500 MB in size contains 500,000sub-watermarks. With only ten different sub-watermarks the resultobtained for the exemplary file is 10500000 different watermarks WZ, W1. . . W3.

If a destination station ZS finds only one or a small number of sourcestations QS1 . . . 3 for the transmission of a file, it is possible thatthe watermark WZ will change only insignificantly during thetransmission U. If, for example, the entire file is transmitted from thesecond source station QS2 to the destination station ZS, then the samewatermark WZ results there as at the second source station QS2, whichwould therefore prevent a unique identification of the station on thebasis of the watermark. In this case the destination station ZSautomatically replaces the transmitted sub-watermarks with new, forexample randomly chosen sub-watermarks. In this way it continues to beensured that the watermarks WZ, W1 . . . 3 of the files present in thepeer network PN are to be uniquely assigned to the respective station.Alternatively it is also possible that in this case the storage stationmakes new sub-watermarks available.

In one embodiment variant, files are made available in the peer networkPN in such a way that one version of the file is provided. When saidversion is distributed in the peer network, a download takes placeautomatically from only one or a small number of source stations QS1 . .. 3 initially. This results in the file automatically being providedwith new sub-watermarks, as a result of which many different versionsare generated in the peer network PN.

In this exemplary embodiment ten different sub-watermarks have beenshown. In order to provide greater security and make a deliberatechanging of the sub-watermarks outside the transmissions U of the peernetwork PN more difficult, a greater number of different sub-watermarkscan be used. These can also be encoded in different ways into the dataof the file.

It is also possible to choose sub-watermarks of different size. Inaddition these can also be used in an overlapping manner. In this caseit makes sense to transmit files in packets whose size is a commoninteger multiple of the sizes of the sub-watermarks. In the case ofsub-watermarks with a length of ten and fifteen bytes the file could betransmitted in packets with a length of 30 bytes or 3000 bytes. In thiscase it also makes sense to arrange the sub-watermarks in the file insuch a way that they always lie completely within a packet, by alignmentwith the packet boundaries for example.

It is possible to prompt the respective source stations QS1 . . . 3 orthe destination station ZS of the peer network PN to communicate theinformation I about transmitted parts of files to the storage station Sby way of an incentive method.

The invention has been described in detail with particular reference topreferred embodiments thereof and examples, but it will be understoodthat variations and modifications can be effected within the spirit andscope of the invention covered by the claims which may include thephrase “at least one of A, B and C” as an alternative expression thatmeans one or more of A, B and C may be used, contrary to the holding inSuperguide v. DIRECTV, 69 USPQ2d 1865 (Fed. Cir. 2004).

The invention claimed is:
 1. A method for identifying a destinationstation receiving a file transmitted in a peer network comprising aplurality of source stations and the destination station, comprising:providing a plurality of copies of a file; generating a plurality ofdifferent versions of the file by assigning a different watermark toeach copy of the file; providing the different versions of the filerespectively from different source stations, such that the watermark ofeach copy of the file is unique to the respective source station;wherein the file is formed from different parts, each part having asub-watermark, for each version of the file, the sub-watermarks of theparts together form the watermark for the version of the file;separately transmitting the parts of the file from at least twodifferent source stations to the destination station, each part of thefile being transmitted with its respective sub-watermark; assembling theparts of the file at the destination station; assembling thesub-watermarks of the parts of the file at the destination station tothereby form a watermark for the destination station; storinginformation identifying the sub-watermarks of the parts of the file; andidentifying the destination station based on the information.
 2. Themethod as claimed in claim 1, wherein the destination station acts as anoriginating station and transmits at least a part of the file togetherwith the respective sub-watermark, to a peer in the peer network, thepeer forms a subsequent watermark unique to the peer, the subsequentwatermark being determined from the sub-watermarks respectivelyassociated with the parts of the file received at the peer, thesubsequent watermark is compared with the information, and theoriginating station in the peer network is determined from a result ofthe comparison.
 3. The method as claimed in claim 1, wherein theinformation is transmitted to a storage station in the peer network forstorage.
 4. The method as claimed in claim 3, wherein the information istransmitted by the source station and/or the destination station.
 5. Themethod as claimed in claim 1, wherein the information is storednon-centrally in the peer network.
 6. The method as claimed in claim 1,wherein the watermark of the destination station is stored as theinformation.
 7. The method as claimed in claim 1, wherein if many partsof the file were transmitted by only one of the source stations, thissource station is considered a primary source station, and thesub-watermarks associated with the many parts of the file are redefinedfor the file at the destination station.
 8. The method as claimed inclaim 7, wherein the sub-watermarks are redefined at the destinationstation based on sub-watermarks received from the primary sourcestation.
 9. The method as claimed in claim 7, wherein the sub-watermarksare redefined independently of the sub-watermarks received from theprimary source station, and the sub-watermarks are redefined by randomselection.
 10. The method as claimed in claim 1, wherein a large numberof sub-watermarks are used.
 11. The method as claimed in claim 1,wherein all sub-watermarks are equal in size.
 12. The method as claimedin claim 1, wherein the sub-watermarks are different in size.
 13. Themethod as claimed in claim 1, wherein each sub-watermark has informationwhich at least partially overlaps a different sub-watermark.
 14. Themethod as claimed in claim 1, wherein each part of the file istransmitted from the source station to the destination station in apacket, and each packet contains the complete sub-watermark.
 15. Themethod as claimed in claim 14, wherein the sub-watermark and the packethave sizes such that the size of the packet is an integer multiple ofthe size of the sub-watermark.
 16. The method as claimed in claim 1,wherein the information is structured in such a way each sub-watermarkis saved in a file with a respective indication of a position of theassociated part of the file within the file.
 17. The method as claimedin claim 1, wherein an identifier of the watermark is stored as theinformation.
 18. The method as claimed in claim 1, wherein eachsub-watermark has a sequential number identifying where the part of thefile fits within the file, the sequential numbers for the sub-watermarksare stored as the information.
 19. A peer network comprising: aplurality of source stations to provide different versions of a file,the different versions of the file being formed by providing a pluralityof copies of the file and assigning a different watermark to each copyof the file, such that each copy of the file has a watermark unique tothe respective source station, wherein the file is formed from differentparts, each part having a sub-watermark, for each version of the file,the sub-watermarks of the parts together form the watermark for theversion of the file; a destination station to separately receive theparts of the file from at least two different source stations, each partof the file being transmitted with its respective sub-watermark, thedestination station assembling the parts of the file and assembling thesub-watermarks of the parts of the file to thereby form a watermark forthe destination station; and a memory to store information identifyingthe sub-watermarks of the parts of the file to identify the destinationstation based on the information.